Turntable drive



Dec. 13, 1949 F. G. BUHRENDORF TURNTABLE DRIVE 2 Shets-Sheet 1 Filed Nov. 15, 1946 1 V l [7| I l l I [LU I HlIJHH a m 5 2a 3 3 a a 4 7 1.. IV 7 9 6 2 M fiv 5 l0 INVENTOP f. G. BUHRENDORF fid ww ATTORNEY F. G. BUHRENDORF Dec. 13, 1949 TURNTABLE DRIVE 2 sheets sheet 2 Filed Nov. 13, 1946 lNl/EN TOR G. BUI/RENDO/PF A ORNEP Patented Dec. 13, 1949 TURNTABLE DRIVE Frederick G. Buhrendorf, Westfield, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application November 13, 1946, Serial No. 709,593

2 Claims. 1

This invention relates to turntable drives and more-particularly to a plural speed drive for a phonograph turntable.

It is the object of this invention to provide a plural speed turntable drive incorporating improved means for effecting a change from one speed to another.

It is another object of this invention to provide a plural speed turntable drive in which the change from one speed to another is made instantly and simply by a reversal of the direction of rotation of the turntable driving motor.

It is a further object of this invention to provide a plural speed turntable drive in which the turntable at any selected speed is driven with minimum variation from constant angular velocity.

In present day reproduction of phonograph records, particularly in the transcription of records for broadcast purposes, it is desirable that the turntable drive be provided with means for selectively rotating the turntable at either 33% revolutions per minute or '78 revolutions per minute in order that different type records may be satisfactorily reproduced at their proper reproducing speeds.

Numerous mechanical drives have been proposed heretofore for this purpose but in these drives, the change from one speed to another usually involves the manual shifting of gears in the drive mechanism to select the appropriate gear ratio to produce the speed desired.

In accordance with this invention the change from one speed to another is made instantly and simply by a reversal of the direction of the retation of the driving motor, which change can be readily effected by operation of a single switch in the motor circuit. In the turntable drive in accordance with this invention, the turntable shaft is driven by either one of two driving shafts, each permanently coupled to the turntable shaft through gears of predetermined ratio. The two driving shafts are located on opposite sides of the turntable shaft and are both rotated by means of a single belt which is pulley coupled to the shaft of a reversible electric motor. An over-runnin clutch is provided in the driving connection between the belt and each of the driving shafts. These over-running clutches are driven simultaneously in opposite directions of rotation for one direction of motion of the belt so that when one clutch is operative, the other is non-operative. Thus, either one of two turntable speeds may be obtained by selection of the direction of rotation of the driving motor.

The invention will be more readily understood by reference to the specification when read in connection with the accompanying drawings in which:

Fig. 1 is a plan view of the turntable drive in accordance with this invention;

Fig. 2 is a side elevation, partly in section, of the turntable drive shown in Fig. 1;

Fig. 3 is a detail plan view of an over-running clutch in accordance with this invention;

Fig. 4 is a side elevation of the over-running clutch shown in Fig. 3; and

Figs. 5 and 6 are plan and side elevations, respectively, of a yieldable coupling element between the driving mechanism and the turntable.

Referring to Figs. 1 and 2, a base I is provided with downwardly extending supportin legs 2 and upwardly extending arms 3, 4 and 5. A mounting panel 6 is attached to these arms.

A plate I is secured to the base I by four resilient mounting elements 8. A bracket I0, supporting an electric motor II, its secured to plate 'I by suitable means. The shaft I2 of motor i II has a pulley I3 mounted thereon. A switch S, Fig. 2, shown mounted in panel I5, is connected in the circuit from an electric power source to motor II. This switch provides means for reversing the direction of rotation of the motor by reversing the current through one of the motor windings. As will be explained clearly hereinafter, the switch S constitutes the sole means whose operation is necessary to change the speed of rotation of turntable I4 from. one predetermined speed to another predetermined speed.

A turntable I4 rests on and is frictionally engagd by the outer ends of spider arms I5, I6 and I1. These arms are integral with and extend outward radially from a flanged end I8 of turntable shaft I9 (Fig. 1). The shaft I9 extends downwardly within a housing I9a, which forms part of and is centrally disposed on the base I. The inner surface of housing Illa constitutes a bearing surface for the shaft I9.

As shown in Fig. 1, a turntable spindle 23, having a "circular flanged base, is secured to the upper end of shaft I9 by means of screws 24. This spindle may be readily replaced by another spindle of different size to accommodate any particular record disc provided with other than a standard center hole.

A unit mechanism for driving the turntable shaft I9 is resiliently mounted at several points 3 gear which is resiliently coupled to the driving shaft [9 through flanged end l8, as will be explained hereinafter.

Two driving shafts 21 and 28 (Fig. 2) are driven from motor I l by means of a belt 20 and pulleys 2| and 22, respectively. As will be explained in greater detail in connection with Figs. 3 and 4, the pulleys H and 22 each drive their respective shafts 21 and 28 through an over-running clutch disposed in housings 30 and 3|, respectively.

Shaft 21 drives pinion gear 33 through a flexible coupling 34 while shaft 28 drives pinion gear 35 through a similar flexible coupling 33. The pinion gears 33 and 35, which are of different diameter, are permanently meshed with a gear 31. The gear ratio between the gear 31 and each of the gears 33 and 35 are selected. to produce the desired speed of rotation of gear 31 when this gear is driven by either one or the other of the two driving shafts.

The teeth of gears 33, 35 and 31 are helically cut. The shafts 21 and 28 are each restrained from axial movement by the spring element in couplings 34 and 36, respectively, and any axial movement of these shafts is clamped by a plunger 9 (one shown) movable in an oil-filled cylinder in the bottom of casing 26. The combined action of the helical gear, plunger and coupling spring provides a low-pass filter which minimizes momentary variation in uniform rotation of gear 31 and shaft 19 as might be caused by slight mechanical imperfections in the driving elements from the power source.

Gear 31 is rotatable about housing 20, a bearing surface for this gear being provided on housing 26 at 49 (Fig. 2). A member 4| is secured to gear 31 to be rotatable therewith. This member 41 has uwardly extending arms 42 and 43 secured thereto. A metal ring 44 is clamped to the arms 42 and 43, as shown. The ring 44 is flexible in the vertical direction but rigid. in the direction of rotation of the gear 31. A cylindrical metal member 45., which surrounds the housing Isa, is provided with a lower flange 46 and means for clamping this flange to ring 44. As shown Fig. 5, two of these flanges are provided on. diametrically opposite sidesof the cylinder 45. The upper end of cylinder 45 is also provided with two flanges 4.1 which are clamped to a second metal ring. 48. On another diameter, the ring. 48 is clamped to the: flanged end It of shaft 19. It is seen, therefore, that the power from gear 31 is transmitted to. shaft I9 through a coupling having high torsional rigidity but sufficiently low longitudinal stiffess to prevent the transmission of vibrations in the drive. This coupling is shown in' greater detail in the enlarged view in Figs. and 6.

As shown in Fig. 1, the belt 20 engages motor pulley I 3 and pulleys 2| and 22. A spring-tensioned idle roller 49 is provided to=maintain constant tension in belt 20. It will be observed that the belt 20 engages the pulleys 2| and 22in a manner to produce rotation of one pulley in a direction opposite to the direction of rotation of the other pulley, that is, for aclockwise rotation of motor'pulley l3, pulley 2l-wil1'receive clockwise rotation while pulley 22 will be rotated in-a counter-clockwise direction.

Referring now to Figs. 3 and 4, the details of a suitable one-way engaging. clutch to be employed in the drive between the pulleys 2|: and 22 and shafts 2.1 and 28, respectively, will be described. As'the same type clutch is used in each case, the details of the clutch associated with pulley 22 and shaft 28 will be described.

It will be observed that the shafts 21 and 28 and their respective pinions 33 and 35 rotate always in the same direction of rotation (counter-clockwise) whether one pinion, for example gear 35, is driving the gear 31 or is being driven by gear 31 in response to its rotation by the other pinion 33. Thus, the gear 31 and, therefore, the turntable is always driven in one direction of rotation (clockwise) for any selected speed.

A gear 50 is secured to the end of shaft 28. Pulley 22 and an annular member 5| secured thereto are rotatable about shaft 28. A rectangular plate 52 is mounted for free rotation on the end of shaft 28. A pair of gears 53 and 54 are rotatably mounted on studs depending from plate 52. Each of these gears is in mesh with gear 50. Gears 53' and 54 have shoes 55 and 56 respectively, secured thereto. These shoes are free from contact with the inner surface of pulley 22 but are so shaped and positioned on their respective gears that they may be brought into frictional engagement with the pulley by rotation of the plate 52 in one direction of rotation.

Two springs 58 and 59, each have one end secured to the underside of plate 52 and their free end in frictional engagement with member 5|. The engagement of these springs with the rotating pulley 22 produces rotation of plate 52 in the direction of rotation of the pulley. Referring to Fig. 3,v a counter-clockwise rotation of pulley 22 produces similar counter-clockwise rotation of plate 52. In this direction of rotation of plate 52, the gears 53 and 54 are rotated about gear 53 in a counter-clockwise direction. Thus shoes 55 and 53 are urged into engagement with pulley 22 and are gripped therein to produce rotation of plate 52, gears 53, 54 and gear 58, which isin mesh therewith. Therefore, for counter-clockwise"rotation of pulley 22, the shaft 28 is drivenin the same counter-clockwise direction to produce clockwise rotation of gear 31 For clockwise rotation of pulley 22,. produced by reversal of the direction of motion of belt 29 the springs 58 and 59 frictiona'lly' engage annular member 5 l, producing clockwise rotational movement of plate 52 and gears 53' and 54 mounted thereon. Because they are in mesh with gear 55, the gears 53 and 54 are rotated clockwise-on their mounting studs. For this-direction of rotation of gears 53 and 54 on their mounting studs, theshoes 55 and 56 are disengaged from frictional contact with the pulley. The pulley thenrotates without power transmitting linkage.

It will be seen from Fig. 1 that thebelt' 2B drives pulleys 2i and 22 simultaneously in opposite directions of rotation, thus rota-ting either one or the other of shafts 21 and 26 for one direction of motion of the belt. Upon reversal of directionof travel of the belt, the previously non-operative shaft is made operative.

In Figs. 5 and 6 an enlarged view of the coupling between gear 31' and shaft i9 is presented. A metal ring 66, secured to the cylinder 45', is of such mass and is so located that the center of percussion of the coupling is at the lower ring 4 4 when the axis of suspension is at the ring 48. A coupling of this type is disclosed and claimed in United States Patent 1,832,285, November 17, 1931, to L. A. Elmer.

While in this disclosure the two driving shafts are gear coupledto the turntable shaft, it will be understood that this invention is applicable to phonograph turntable drives in which the turntable is-rotated by a plurality of turntable-engaging friction wheels of different diameters mounted on the individual driving shafts.

What is claimed is:

1. In a two-speed power transmission system, a driven shaft, a pair of driving shafts each having one end coupled to said driven shaft through gears of selected ratio and each provided at its free end with a gear, a separate coupling associated with the free end of each of said driving shafts, each of said couplings comprising a hollow pulley, a freely rotatable gear mounted within said pulley in mesh with the gear on the free end of said driving shaft, said freely rotatable gear being provided with a shoe surface over a portion of its periphery adapted to frictionally engage said pulley for one direction of rotation thereof and to disengage from said pulley for a reverse direction of rotation thereof, and a single reversible power transmitting means for rotating the pulley elements of said couplings simultaneously in 0-pposite directions of rotation for one direction of travel of said power transmitting means.

2. In a turntable drive, a turntable shaft, a pair of driving shafts each coupled to said turntable shaft through gears of predetermined ratio, a reversible driving motor having a shaft, a pulley secured to said motor shaft a separate coupling associated with each of said driving shafts, each of said couplings comprising a hollow pulley rotatably mounted on said driving shaft and a oneway engaging clutch disposed in said hollow pulley and forming the sole driving connection between said pulley and said shaft, and a single belt connecting said motor shaft pulley with said coupling pulleys in a, manner to produce simultaneous rotation thereof in opposite directions for one direction of motion of said belt.

FREDERICK G. BUHRENDORF.

REFERENCES CITED The following references are of record in the file of this patent: 

